1. Field of the Invention
The present invention relates to a photoelectric conversion device and image sensing system.
2. Description of the Related Art
Recently, as described in Japanese Patent Laid-Open No. 2004-186407, photoelectric conversion devices are achieving higher pixel densities and smaller chip sizes, and the area of the photoelectric converter (e.g., photodiode) is tending to decrease. Japanese Patent Laid-Open No. 2000-252452 discloses a photoelectric conversion device having a plurality of wiring layers.
As shown in FIG. 12, a photoelectric conversion device disclosed in Japanese Patent Laid-Open No. 2004-186407 has a pixel area A1 where photoelectric converters PD are arranged, and a peripheral circuit area B1 serving as the peripheral area of the pixel area A1. The peripheral circuit area B1 is shielded from light. In the pixel area A1, one metal layer 5 and one polysilicon layer 2, in other words, a total of two wiring layers are arranged. In the peripheral circuit area B1, two metal layers 5, 7 and one polysilicon layer 2, in other words, a total of three wiring layers are arranged. Since the numbers of wiring layers in the pixel area A1 and peripheral circuit area B1 are different from each other, it is difficult to satisfactorily planarize the entire top faces of planarized layers 3 and 13 arranged on a passivation film 11. In this case, the planarized layers 3 and 13 must be made thick. Steps SD1 and SD2 sometimes appear on the top faces of the planarized layers 3 and 13. This makes it difficult to apply the materials of color filters 8a and 8b and microlenses 9a and 9b to uniform thicknesses. As a result, the thicknesses of the color filters 8a and 8b and microlenses 9a and 9b may vary.